A cursory glance at the cast list for this pricey West End opening suggests it might be a comic treat. Fans of TV’s The Inbetweeners, Toast, Fresh Meat and Plebs will certainly be enticed by the presence of Simon Bird, Matt Berry, Charlotte Ritchie and Tom Rosenthal. But after a promising first few minutes it turns out to be a woeful dud, in which the flashes of wit in Christopher Hampton’s Seventies play are routinely missed.

Bird plays Philip, an unworldly academic who can’t teach literature because he’s incapable of being critical. Instead he specialises in the study of language, with a stale penchant for anagrams. Fond of exchanging quips with his slothful colleague Donald (Rosenthal), he initially comes across as an amiable loser, like a less sarcastic version of Bird’s Inbetweeners character Will.

Though smitten with Ritchie’s Celia, Philip is all too easily seduced by lonely Araminta (an effortlessly stylish Lily Cole, adopting a bizarre cut-glass accent). Meanwhile Celia falls under the spell of arrogant writer Braham, played by Matt Berry, whose usually glorious voice never really works its fruity magic here and is outdone by his loud magenta three-piece suit.

Hampton’s key idea is that Philip’s inability to exhibit even a hint of misanthropy causes mayhem rather than bliss. As he tries to make everyone happy but blunders deeper and deeper into the emotional wilderness, his haplessly non-judgemental manner should be profoundly sad. At the same time the smug insularity of those around him ought to appear beguilingly surreal.

Yet while Simon Callow’s production is easy on the eye — mainly thanks to Libby Watson’s elegant design — there’s little else to admire. There’s no chemistry between the performers, who often look ill at ease. The result is two very long hours, stilted and lacking theatrical vitality. As joke after joke fails to land the play ends up seeming thin, dated and tedious. The whole venture feels misconceived.